The present invention relates to data storage, and more specifically, this invention relates to data storage having prioritized backups on a disk level within a storage system having multiple data storage devices.
Disk errors in enterprise storage, e.g., large storage products, may result from a number of different causes including hardware failures (e.g., physical disk and/or adapter), an unsupported disk model and/or firmware level, operating system failures, erroneous storage application code, etc. Thus, while some errors may be caused by a more serious situation, others may simply result from normal disk operation.
Moreover, when a disk error occurs, the disk may issue an ‘alert’ regardless of how serious the error. However, it would be unfavorable if the storage system failed every disk that had an error, as this would increase operation costs, decrease efficiency, etc. Therefore, conventional products must determine whether a disk is actually faulty, or just experiencing errors typical of normal disk operation.
As a result, conventional products maintain two copies of data on a given disk such that, if the primary copy of the data is lost or corrupted for any reason, the backup copy is used to replace the data. However, this scheme reduces the overall capacity of conventional storage systems to 50% of the disk capacity. Furthermore, it is still possible to lose both copies of the data, or to find that the two copies of the data differ without a clear understanding of which of the two values is the correct value.